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So, what is the difference between S, RS, RT, GS, etc? I know the differences in the /'s.. but what do these other designations mean?

S, RS, and RT are TRIM variations on the same bike.

Different fairings plus bars, etc. to match

For R100s except for 1977 and 1978 the drivetrains are identical in a given year. In a given year there was only ever one R80 variant.

GS is an entirely unique, smaller frame shared with R100R.

G/S frame was similarly shared with ST.

Pre '85 R65 were a third unique frame. Post '85 R65 frame is same as R80, R100.

Big frame bikes were called /7 through 1980, and this includes S, RS, and RT.

Bikes were substantially modified from /7 configuration in 1981 and again in 1985. Were the same 1985-1995.

R80 and R100 engines are identical except for cylinder barrels and pistons. Same crank, same stroke. All bikes have same transmission but R80 bikes have different rear drive gearing than R100 bikes. In '77 and '78, R100/7 have different rear gearing than others, as they are lower powered, with lower compression and smaller carbs.

New/old 1977 R100/7 Help

Bought a R100/7 out of a garage. Think I have all the parts. Cylinder heads were removed along with mufflers. 43,000 on the odometer. True/false? Looks like a lot of leaking was going on but no wreck indication except small scratch on crash bar. Seat does not show a lot of wear. Luftmeister fairing some scratches but no evidence of cracks or breakage. I think the heads were pulled to maybe replace gaskets. Valves need cleaning, piston head needs cleaning. Cylinder heads smooth inside and rings feel sharp to the touch. My first BMW was a Daytona Orange 1976 R90S. Sold it when I got married. Don't have the bike or the wife Rats. Ennywho, The bug bit me so I am thinking rebuild. Is a total rebuild reasonable if I do the work myself? So far I see no broken big items, I just don't know why the Jugs were pulled. What are your thoughts? Been with MOA since 2003 and really don't know where else to go except AdvRider. Maybe just part it out? Please advise. Thank you.

Is a total rebuild reasonable if I do the work myself? So far I see no broken big items, I just don't know why the Jugs were pulled. What are your thoughts? Been with MOA since 2003 and really don't know where else to go except AdvRider. Maybe just part it out? Please advise. Thank you.

If it's mostly there and you have the skills to do the work, parting it out would be the last thing I would consider. It's definitely rebuildable...it's just going to take time and money. You haven't said (or possibly know much) about the transmission. There's also the wheel splines...they'll probably be OK. You might need to replace the wheel bearings. Given the unknown state of things, you might end up replacing even things like the clutch unless you want to clean it up and take your chance...you can determine if it needs replace later if it doesn't work right. Just don't get too far from home on that first ride!!

It's a labor of love... and your labor will be worth $0.00/hour. The trick is to keep the parts bill within reason and avoid the nasty surprises (compression, oil pressure, missing parts, etc). Electrical part prices are getting crazy ($95 for a turn signal flasher? !), you can expect to replace a lot of rubber bits and the cost of paint work can be a challenge. However, it's rewarding when you are finished. It's like getting rescue dog from the pound who becomes a companion for life.

You are at a disadvantage because the bike is apart. However, if the price is right you can save another airhead from the people who would part it out. It belongs on the road.

I am not sure whether the original question was about the difference in nomenclature only or also about the difference in technical detail. And there is a ton. When I brought my R100S back to life after over a decade of hibernation, I found out that many parts were different from the standard 100/7 and 100RS and RT other than just the obvious bodywork. Exhaust, final drive, carb jetting, just to mention a few.

77-78 may have been a high point, but rear drive of 100S is same as RS as are the carbs. From factory, that is. Yes, there are the 40mm exhaust versions and the "squish band" versions, but these are few and far between despite all the talk about them. Yes R100/7 for 2 years had small valves, small carbs and lower compression and lower final drive, but these distinctions were gone in '79.

77-78 may have been a high point, but rear drive of 100S is same as RS as are the carbs. From factory, that is. Yes, there are the 40mm exhaust versions and the "squish band" versions, but these are few and far between despite all the talk about them. Yes R100/7 for 2 years had small valves, small carbs and lower compression and lower final drive, but these distinctions were gone in '79.

Well, as far as the rear drive is concerned, all RSes had rear discs, some Ses such as mine, had a rear drum